A Breakthrough in Harnessing the Stars

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Charlie Rapheal, Editor

Recently, a breakthrough in nuclear fusion was made. Scientists at the Joint European Torus (JET) lab in Oxfordshire, England have updated the record for energy created through nuclear fusion. The experiment produced 59 megajoules of energy over five seconds and 11 megawatts of power. This is around double the previous record. 

If we can maintain fusion for five seconds, we can do it for five minutes and then five hours as we scale up our operations in future machines ”

— Tony Donne, EUROfusion Program Manager

The nuclear energy that we see today is generated through a process called nuclear fission. Simply put, nuclear fission is the splitting of large radioactive atoms, and in turn releasing energy in the form of heat. There are different types of reactors that capture this heat in different ways, but one of the ways of doing it is in boiling water. These types of reactors are called boiling water reactors (BWR). The water, once boiled, turns a turbine as it evaporates and the turbine spinning is what generates power. The turbine is actually very similar to that of a wind turbine. Nuclear fission also creates a type of nuclear waste that is very difficult to get rid of, and this waste is one of the biggest challenges and critiques to fission reactors. 

Nuclear fusion, however, is the opposite. Fusion works by joining smaller atoms together instead of splitting them, and it is much less polluting and dangerous. It’s the type of energy release that stars, like our sun, emit. In stars, there is extreme pressure and temperature that allows this fusion to happen very easily. Because our planet is much colder and has much less pressure than the middle of a star, mimicking this environment that allows these atoms to join together is very difficult. This is why there are no nuclear power plants around the world that use fusion, only fission. 

Employees work inside the ITER (International Thermonuclear Experimental Reactor) construction site where will be installed the Tokamak, a confinement device being developed to produce controlled thermonuclear fusion power (CHRISTOPHE SIMON via Getty Images)

JET’s breakthrough is the next step at changing that. Scientists developed a donut-shaped reactor that houses plasma and allows these atoms to split. Since the pressure here on Earth is so much lower than it needs to be for this to happen, the reactor needs to be capable of reaching temperatures higher than those in the center of stars. The reactor quite literally needs to be hotter than the sun. 

The breakthrough is also important because it helps lay the groundwork for the construction of ITER, which is a new fusion reactor being built in France. ITER will be much bigger than JET and, because of the progress in research that JET has made, will be much more efficient. It’s hard to get a good idea of just how efficient these reactors are, but there is a simple and helpful measurement that can help explain: q value. A q value is a ratio of how much energy was produced compared to how much energy was put into the reactor. For 5 seconds last week, the JET reactor ran at a q value of about .3. A good way of thinking about this is that this means that the reactor produced about 30% of the energy that was put into it. The highest q value ever recorded was .7, but that was for a few billionths of a second. A reactor running for 5 seconds at a q value of .3 is much more meaningful.